Delfas joins from the Financial Conduct Authority where she heads the international unit. Delfas succeeds Caroline Wayman, whose departure after seven years had already been announced.

"Nausicaa officially takes up the role on 17 May and will be in post while the Financial Ombudsman Service's board carries out an open recruitment process for a permanent chief executive and chief ombudsman," the FOS said in a statement.

(Reporting by Huw Jones, editing by Louise Heavens and Catherine Evans)